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Could a Personal Locator Beacon or EPIRB carried by a passenger aid in locating a downed airliner?
There've been a lot of questions lately about tracking aircraft, and after a conversation with a friend of a friend I started wondering:
Could a PLB or EPIRB carried by a passenger or crew member aid in locating a downed or missing airliner? There are a dozen or so brands out there, most using similar technology, like this ACR ARTEX unit:

Now, I'm well aware of the FAA and FCC regulations about electronic devices in flight, and that's not what I'm interested in. I also realize that airliners already carry an ELT.
If a paranoid passenger brought one on board, would these devices function at all from inside an airliner cabin? Some feed GPS location data to a 406MHz locator beacon, and those would potentially be less useful (as they'd have to be at hand and probably triggered manually. Others, like the Spot GPS tracker, have the ability to upload GPS track data on the fly to satellite communications networks such as Iridium.
I'm personally skeptical, given that GPS generally needs a clear view of the sky and that a fuselage seems likely to block or reduce a 406Mhz ELT signal, but I'm curious to know if there's any information out there.

GPS works reasonable well inside an aircraft if you are at a windows seat. On every flight I have a GPS tracker running on my phone or tablet and the track is intermittent but definitely usable. I am not sure about 406MHz or Iridium transmissions from inside.

It don't see why not, but from inside the fuselage the 406MHz signal will be attenuated very much, so I doubt whether the satellites will be able to locate it.

Relatively short answer
Cospas-Sarsat: Feasible but...
It's possible, but there are many individual elements involved. It's a matter of probability that most of the time there will be a combination preventing the link to work. If you know what to do and take care of ensuring a good direct line of sight (LOS) you may be able to avoid some of these combinations. It cannot work underwater.
Parameters that can attenuate the signal reaching the satellite receiver are of different origins:

The aircraft design itself (composite materials or aluminum, number of windows, ...)
The location of the accident (canyon, trees, ...)
The transmitter use (position, window proximity, metallic surface or debris interference, body proximity, ...)

I'm not aware of experiment results for using a PLB within a metallic container like a commercial aircraft cabin. It's still possible to evaluate the RF channel loss in different configuration and see if the signal can reach the receiver with the minimum required level.
As explained in the next sections about the Sarsat satellites of the international SAR service on 406 MHz:

The threshold for signal reception by the receiver is 161 dBW.
With an initial power of 7 dBW (5 W), the attenuation must be at most 168 dB
In good conditions we can expect an attenuation of "only" 148.1 dB. Such signal 12.9 dB stronger that the threshold can be detected easily.
In degraded conditions we may experiment an attenuation of 177.5 dB. Being 9.5 dB below the threshold, this signal is not detected.

Indoor transmission put the system at its limits of detection capability (a S-meter unit is 6 dB).

Weak signal on a S-meter, S-unit is 6 dB (source)
Many small attenuation causes that, when summed, can prevent the link to work must be taken into account, hence this answer is a long one.
SPOT LLC
SPOT LLC solution you mention is a commercial messaging initiative working on 1.6 GHz, out of the Cospas-Sarsat system. Higher frequency means higher attenuation. The limited 0.4 W RF output also makes the signal weaker. It's very unlikely that SPOT could work within the cabin.

Details
Introduction: PLB principles
Emergency PLB operate on 406 MHz. The previous 121.5 MHz civil frequency is not monitored anymore by SAR satellites, but can be used (in addition of the actual signal at 406 MHz) as a homing guide for the SAR team. They are informed about whether this homing feature is active or not by the message sent by the PLB.

PLB output power is 5 W (equivalences: 7 dBW 37 dBm) at 406 MHz, in vertical polarization.
From C/S T.004, the performance of the satellite system is:

A "probability better than 95% to provide a valid solution (15 hexa identification provided) for a beacon transmitting with a 37 dBm output power (with a whip  antenna) and for satellites passes with elevation above 5°)"
A "probability better than 95% to provide a Doppler location with an accuracy better than 5 km"

There are no satellites entirely dedicated to the SAR service, rather distress signal receivers are carried as one of the payloads aboard satellites. The system is made of two constellations:

GEOSAR constellation, Geostationary Earth Orbit SAR. These satellites are at fixed positions, 36,000 km above the equator, and are covering the globe except the polar regions.
LEOSAR, Low Earth Orbit SAR. Satellites in near-polar (about 85°). LEOSAR is made of two sub-constellations: Sarsat satellites orbiting at 850 km, and Cospas satellites orbiting at 1,000 km.

(Source)

A third constellation is planned to operate at a higher altitude than LEOSAR (MEOSAR, currently not fully deployed).
While GEOSAR are likely to be first to detect the PLB activation due to their permanent LOS, LEOSAR will provide the best detection due to the shorter distance to the device.

I'll focus on LEOSAR / Sarsat payload which provides the best chances for the detection of a PLB signal partially blocked by RF impermeable obstacles.
Sarsat payloads
Satellites carrying a LEOSAR Sarsat payload are NOAA 15 (Sarsat 7), NOAA 18 (Sarsat 10), NOAA 19 (Sarsat 12). Other are scheduled to be active in the future (some may be already, I haven't checked). They are fitted with a SAR receiver (search and rescue processor, SARP). Sarsat satellites can be tracked on N2YO.com.
According to Cospas-Sarsat LEOSAR Space Segment Commissioning Standard - C/S T.004, a SARP-2 has a sensitivity of -161 dBW, and SARP-3 -164 dBW (that's about 60 attowatts to be compared with a cellular phone cell: -134 dBW, 1,000 times less sensitive).
Can this small quantity be delivered to the SARP from the inside of a cabin?.. This is a matter of knowing the initial power, and determining the loss along the wave path until the signal reaches the receiver.
The power generated by the transmitter amplifier is 5 W, or 7 dBW. 161 dBW on the receiver means receiving a 1 W signal that has been attenuated by 161 dB. If we have already 7 dBW at the source, we can bear a maximum attenuation of 168 dB.
Main loss inventory
Propagation loss in direct view
The most important part of the signal will be lost in the atmosphere between the antenna of the PLB and the antenna of the SARP.

Loss due to distance
Loss is dependent on two factors: distance and wavelength. Both factors limit the area of the receiving antenna compared to the whole sphere of the wave front, and in consequence the portion of energy received is smaller too.

Using the propagation model ITU-R P.525 (free-space propagation).
Distance = 850 km, f = 406 MHz.
Assuming isotropic antennas for the time being.
According to the model, the loss (dB) is:
Lbf = 20 log(4πd/λ)
.   = 32.4 + 20 log(f) + 20 log(d)
.   = 32.4 + 20 log(406) + 20 log(850)
.   = 143 dB

The signal that left the PLB antenna reaches the SARP antenna -143 dB weaker, assuming the best antenna alignment. But this is never the case, because when in a polar orbit, the satellite is unlikely to be exactly above the beacon.
Misalignment of the receiving antenna
There will be an angle between the nadir of the SARP and the beacon. This off-nadir angle, depends on the actual track of the satellite for the current orbit:

Target off-nadir
The gain of the antenna varies according to this angle. Sarsat-TIROS SARP Receive Antenna (UDA) Gain Pattern:

UDA antenna gain at different off-nadir angles (source)
Assuming the polarization is favorable (RHCP), the gain may varies between +2 dB and -10 dB. Note that:

The gain is better when the off-nadir angle is large. This is likely to compensate the higher distance to the beacon.
I'll assume a link length f 850 km, but the actual length is larger when the beacon is not directly at the satellite's nadir.

We should now work with the probability distribution of the misalignment for the LEOSAR antennas to have the full range of possibilities and their likelihood (e.g. Monte-Carlo simulation). To simplify, let's just use a bad case: -4.4 dB (this is not the worst possible). Loss so far: -147.4 dB (-143 - 4.4).
Attenuation due to feeder and duplexer
On the satellite, the SARP is connected to an antenna via a duplexer to isolate the SARP uplink antenna from the SARR downlink signal (SAR repeater used on local mode, not detailed here):

Hardware on the Sarsat satellite (source)
The duplexer + feeder loss is -1.6 dB. Loss so far: -149 dB (-147.4 - 1.6).
Loss margin left
We had a budget for -168 dB loss, we have used -149 dB. The margin until the PLB signal is lost by the SARP is 19 dB, assuming we are in this configuration:

PLB is outdoor.
The LOS is completely clear, no foliage, no roof, etc.
PLB antenna has no gain/loss (0 dB gain).
PLB antenna is vertical, this is the normal use of the SAR device.
PLB antenna and RF output stage impedances match (no SWR).
There is no atmospheric loss (free space)

Additional losses
It's time to re-look at the assumption made until here, and take into account the additional effects encountered when the PLB is used from the cabin of a crashed aircraft.

PLB is outdoor.

Actually the PLB is behind a cabin window.
From Arkema:
"Most formulations of colorless Plexiglas sheet readily transmit standard broadcast, television and most radar waves of the electromagnetic spectrum". It can been assumed that windows (including the internal protection sheet) don't block the PLB signal. Loss = 0 dB.
In the cabin, numerous reflections will occur on the wall, and due to the closed space with only small windows, it's likely the reflected signals will globally interfere in a destructive way (phase mismatch) with the original signal.
If the PLB is displaced, even by a small amount, the reflections are changed. The RF energy actually vary continuously, creating a fading effect. Reflections has been studied in somehow comparable environments, for UHF frequencies. While the frequency was a bit higher, and the environment was a simple one, we can use the results for a rough order of magnitude:

RFID signal (915 MHz) loss due to reflections (source)
The spatial fading is visible, at some distances reflected signals add, at other they subtract. This loss is also known as multipath effect. The signal may be attenuated by 10 dB or more compared to free space.
Each reflection has also the potential to change the polarization. See next point.

PLB antenna is vertical, this is the normal use of the SAR device.

The transmitter and receiver antenna polarization must match or an attenuation occurs. The polarization of an antenna describes the plane in which the electric field is transmitted. For a simple antenna, made of a single active element, the electric field is sent in the plane of the element:

Vertically and horizontally polarized waves (source)
Vertical polarization creates less reflection on the ground, which is usually what is desired, so a PLB creates a vertical polarization, but only if the antenna is kept vertical, else the polarization will follow the antenna orientation.
To cop with both linear vertical and horizontal polarizations, and everything in between, the SARP antenna is designed to be circularly polarized, and is able to receive both in good conditions, but not optimal conditions:

linearly polarized antennas will work with circularly polarized
  antennas and vice versa. However, there will be up to a 3 dB loss in
  signal strength. In weak signal situations, this loss of signal may
  impair communications (source).

The antenna on the satellite should be like this:

Helical, circularly polarized, antenna (source)

The LOS is completely clear, no foliage, no roof, etc.

Indeed, if there is a metallic obstacle in the LOS and there is no possibility for reflections (no hole in the metallic cabin), no signal is transmitted. This could happen if the PLB were surrounded by metallic debris from the airplane wreckage.
Else there is a volume (the Fresnel zone) between the transmitter and the receiver that must be free of obstacles. This zone is an ellipsoid around the LOS. If obstacles are present there will be diffraction and reflection. Diffraction scatters the signal (no need to have knife-edge corners), and reflection deviates it, which could be a positive effect when there is no clear LOS.
Dense vegetation or heavy foliage on the LOS: There is water in plants, a loss occurs, typically larger than 0.1 dB/m at 406 MHz. We can use models to evaluate the attenuation:

(Source, page 155)
Example: The aircraft crashed in a forest. The aircraft is surrounded by 25 m trees, except in the direction from which it came.
Satellites low on the horizon will not be accessible: GEOSAR satellites over the equator are usually low on the horizon when viewed for medium latitudes, and some orbits of LEOSAR will be hidden by the trees due to the loss exceeding -15 dB as soon as the depth of foliage is 50 m (slant depth). This depth can be quickly encountered, leaving a small free field of view from a window (it would be larger for the windshield though):

Tree trench created by crash-landing in a forest

PLB antenna has no gain/loss (0 dB gain).

This is likely the case for many PLB. PLB antenna seems to be a shortened 1/4 λ whip. Antennas are measured against an hypothetical perfect antenna (isotropic antenna), and the ratio of amplification is expressed in dBi (dB comparing to isotropic). dBi and dB are equivalent in the current discussion as the isotropic antenna has a gain of 0 dB.

PLB antenna and RF output stage impedances match (no SWR).

In order for the current out of the PLB RF amplifier to be radiated entirely by the antenna, PLB output impedance and antenna impedance must be equal. As soon as there is a mismatch, a part of the RF current is not converted into an electromagnetic wave and returns to the amplifier, mixing with the current flowing in the other direction. The result is the appearance of standing waves in the PLB device. The ratio of SW is smartly named SW ratio (SWR). PLB are stated having a SWR less than 1.5 or 2 in their specifications. The corresponding loss is 0.2 and 0.5 dB. Not so much.
The impedance of the antenna varies greatly as soon as the antenna is not in a free space. A common cause is that a part of the body (containing water) is close to the antenna, or touching it. This could easily lead to a loss of 10 dB. The radiative efficiency of the antenna (gain) also suffers: Touching the antenna is like deforming it. Its characteristics are changed. For example is is no more optimized for the signal frequency to radiate. So in addition of SW appearance, the current that reaches the radiator is also poorly converted into waves. In your scenario it is important to use the PLB as intended, the antenna being unobstructed.

There is no atmospheric loss (free space).

This is another effect difficult to estimate, as it varies with time of the day, weather aspects and Sun activity.
Oxygen and water vapor play an important role. From ITU-R P.676-10:

Attenuation in dB per km (source)
It seems for UHF the absorption is rather limited, so let's ignore it.
Other losses are due to sporadic electrical activities in the ionosphere. They are more difficult to estimate, and they translate into noise rather than attenuating the signal received by the SARP. Other elements like the capability of the SARP to reject noise would also need to be considered.
Ionosphere anomalies could potentially introduce errors in the Doppler localization.

Bottom line
Let's recapitulate the losses we have discussed:
 - Impedance mismatch / SWR:                 -0.5 dB
 - Transmitter antenna gain:                 +0 dB
 - Reflection in the cabin:                  -0 to -10 dB (center).
 - Cabin window:                             -0 dB
 - Fresnel obstruction and trees:            -0 to -15 dB
 - Free space loss:                          -143 dB
 - Absorption by atmosphere gases            -0 dB
 - Other propagation losses:                 Not evaluated.
 - Off-nadir angle:                          -0 to -4.4 dB
 - Linear to circular polarization mismatch: -3 dB
 - Satellite duplexer:                       -1.6 dB

                               Acceptable:   -168   dB
                               Best case:    -148.1 dB
                               Worst case:   -177.5 dB

The worst case is encountered when:

The PLB experiments the higher level of reflected waves. This can be eliminated by being very close to the window, and shielding the rest of the cabin with something metallic, but not too close.
The Fresnel ellipsoid is blocked by trees. Not much freedom here. LEOSAT will hopefully have orbits with sufficient high elevation to be out of the obstacles. If the aircraft is really covered by deep foliage, there is no much chance for a successful link.
The aircraft is at the nadir of the satellite. The SARP antenna is optimized for off-nadir locations (no sure off-nadir locations will be better served, due to the increased slant distance, that would need to be checked). Too bad if the aircraft is in a forest.

Note that carrying a personal locator doesn't cause a safety problem, as it doesn't transmit before being activated. Activation will be either manual (usually for PLB) or by sensing a large acceleration (seems limited to ELT). I don't know if the security guys at the airport will let you board with a transmitter. It should be easier to persuade the pilots.
Case of a SPOT device
Compared to the numerous documents that describe governments-financed SAR service on 406 MHz, SPOT is a more confusing solution.
This is not related to SPOT, the observation satellite family built by Astrium. GEOS IERCC (International Emergency Response Coordination Center) has no link with the GEOS satellites family launch by Nasa some decades ago. It is not either GOES, the geostationary satellites that support GEOSAR.
Globalstar is a large satellite phone company owning satellites. SPOT LLC is a subsidiary of Globalstar providing satellite data links and related sets for messaging and voice communications. GEOS-Alliance has launched a privately-owned assistance service based on SPOT capabilities. GEOS-Alliance services are sold online, and by retaillers.
From SPOT website:

SPOT Gen3 provides location-based messaging and emergency notification
  technology that allows you to communicate from remote locations around
  the globe. It offers custom tracking interval options,
  motion-activated tracking, long-life battery and more.

In short:

Instead of buying a SAR transmitter and then having the service for free, the GEOS-Alliance subscriber receives a transmitter and pays an annual fee.
Instead of having the SAR device connected to the SAR organizations worldwide through the LUTs and MCCs/RCCs, the subscriber is connected to GEOS which calls the local emergency services on your behalf.

The technology behind:

SPOT/Globalstar seems to use LEO spacecraft at 1,414 km instead of 850 km for Sarsat, with a 52° inclination instead of 85°, meaning their coverage could be reduced.
SPOT messengers are limited to 0.4 W instead of 5 W for Sarsat, maybe because of regulations, as they can be used without actually signaling a distress situation.
Globalstar frequency used is 1.6 GHz, instead of 406 MHz for Sarsat.

It seems that these three technical differences are not going to make SPOT devices as efficient as Sarsat:

Using the same ITU-R P.525: Lbf = 20 log(4πd/λ) gives a free space loss of 159 dB upfront, to be compared to the 143 dB for Sarsat (difference: -16 dB).
0.4 W = -4 dBW instead of 7 dBW for Sarsat (difference: -11 dB).
We may add a loss of 1 dB for the atmosphere absorption at this frequency.

If I'm not wrong, that's already a difference of -28 dB at the receiver. It must be very sensitive, or be liked to hi-gain antennas to compete with the governments-operated SAR. That's not going to make it from within the cabin of an aircraft with a limited LOS, and sometimes this seems to even not work well in the open space.

Reference documents

C/S A.003: Cospas-Sarsat System Monitoring and Reporting
C/S G.003: Introduction to the Cospas-Sarsat System
C/S G.004: Cospas-Sarsat Glossary
C/S G.006: Cospas-Sarsat System Assessment
C/S G.008: Operational Requirements For Cospas-Sarsat Second Generation. 406 Mhz Beacons
C/S T.001: Specification for Cospas-Sarsat 406 MHz Distress Beacons
C/S T.003: Description of the Payloads Used in the Cospas-Sarsat LEOSAR System
C/S T.004: Cospas-Sarsat LEOSAR Space Segment Commissioning Standard
C/S T.011: Description of the 406 Mhz Payloads Used in the Cospas-Sarsat GEOSAR System

More Sarsat documentation: Cospas-Sarsat site

Actually things are common knowledge, but if you want to clarify or have and external confirmation I'm interested in sources discussing transmit performance through an aircraft cabin, mostly. I get the theory, and everything you said agrees with what I know, but I haven't been able to find any articles or other information actually stating whether or not your PLB signal would ever reach a satellite from inside an airliner cabin.

@egid: Done! Feel free to tell me if something seems wrong.

Did you.. did you really call this a "relatively short answer"? EDIT: Yeah, you did. I checked. It took me a couple minutes of scrolling tho. xD

If this isn't the best explained and made out answer on Aviation SE, I don't know what it. Did you create those illustrations yourself for this answer?

@Firee: Thanks :-) I draw some of them with Inkscape.

@mins "The threshold for signal reception by the receiver is 161 dBW" Shouldn't that be -161 dBW?

@AndrejaKo: Yes, of course, a positive ration for dBW would mean the signal is larger than 1W.

I have a SPOT Beacon that I use for occasional adventures: mostly flying small planes and kayaking.  But its small enough I generally carry it with me when I fly commercial.

Because it connects to satellites, no one needs to be nearby to "hear" it.  I can press the SOS button most anyplace in the world and summon help.
There are some remote parts of the ocean where there is not good satellite coverage, (see the coverage map), but generally it may help in an emergency.
I don't know if such a device would work from inside a commercial airliner.
I do know I've been able to get GPS signals by pressing a GPS receiver up against a cabin window, but it is slow to acquire the GPS lock.  I don't know if it could transmit to the satellite network through the cabin window.

Unfortunately it doesn't work underwater. The min/max operating altitude range is -328ft to +21,320ft.

That is getting pretty pedantic:  SPOT messages their monitored service, who calls and coordinates with S&R.  SPOT has many documented saves.

On my SPOT, I set my profile to explicitly state that I'm a pilot, flying.  I try to update it for a current flight plan and tail number on each flight.  And based on SPOTs rescue history: they do take reports seriously.  (Okay... maybe not if the report is coming from the interstate on a clear day.  But if there is no reason to distrust the report, they do, in fact, follow up aggressively).  Other info on that page is misleading, such as: SPOT has 400mw, but EPIRBS have 5W!  (enough power to reach the satellite network is enough... more is not better)

I will add that my phone's GPS does receive signal when within an airline cabin, at least when sitting in the window seat and holding the phone in normal positions in front of me (not pressed up against the window).

This answer doesn't seem to say anything more than "I saw this package at CostCo and I read the brochure, and listen to me defend my purchase with stuff out of the brochure". It does not reflect even awareness that SPOT is a commercial knock-off of a better system - the system OP is asking about, by the way, which makes this OT and kind-of an advert. Imagine if you saw a question about making orange juice with Seville oranges, and an answer sung the virtues of Tang...

For instance "no one needs to be nearby to 'hear' it, I press the SOS button most anyplace" facepalm, ELTs do not work that way, sigh. Spot isn't bringing anything to the table. Also the way that sat-map is drawn uncovers the entire Pacific Ocean, so Hawaii, Guam, Midway, Java, fuggedaboutit. Which is a huge disadvantage.  As for "I don't know", why post then?  This really is just "I have spot, spot is awesome".

These personal locator beacons actually operate via the Cospas-Sarsat system of international search & rescue beacons, nothing to do with Iridium which is a commercial system. The have been known to transmit a signal perfectly well through things like a locked metal cabinet in a basement of a house with the antenna retracted and still summon help, in that case by error though.

could you provide some links/sources?

"They have been known to transmit a signal perfectly well through things like a locked metal cabinet in a basement of a house with". Ah that will be a problem for engineers in charge of shielding devices. If waves now exit a  metallic box, it's likely they will also enter cable shields or things like that.

What you say is only true for 406MHz ELTs. There are competitors trying to sell a commercial version that piggybacks on the sat phone networks. SPOT being the most visible example.  They've gotten in trouble for saying theirs is comparable to a 406, though their ability to do routine pings means it leaves a trail of breadcrumbs. @mins don't discount Dave's experience; probably the most common call the ELT responders make is to airport groundskeepers to investigate an ELT beacon going off in a GA hangar.  Most GA hangars are corrugated steel roofs and walls.

@Harper: I agree a small signal may escape as soon as the enclosing walls don't create a good Faraday mesh, but definitely not supporting ELT being "known to transmit a signal perfectly well through things like a locked metal cabinet in a basement of a house with the antenna retracted". This can be easily confirmed by wrapping a smartphone into aluminum foil.

@mins ... or wrapping it in the building I'm in right now - I get the idea.  On the other hand, "Find My Phone" worked (2-way) with my phone inside the money safe at a restaurant!  If I read between the lines, I think Dave is telling us about the time the fire department showed up owing to an ELT going off in a gun safe in the basement.  Just because signal doesn't usually get out, doesn't mean it never does or can't - that seems proven. ELT is much lower frequency , and will try, try, try.

@Harper: The shorter the wavelength, the worse the Faraday effect of an incomplete cage (as soon as the hole in the cage is larger than the wavelength, some electric field enters/escapes the cage). So what blocks a 1.8 GHz --or whatever "4G" (LTE) frequency used locally-- cell phone signal will better block a 406 MHz SAR signal.

ELTs do not normally use GPS. There are newer GPS reporting devices that do use GPS, although they cost more. They work inside vehicles because the signal goes through the window. Commercial planes usually have 2 of them, one in the tail and another portable one in a forward locker or bin. Feel free to bring a bag of them onboard. Do not accidentally activate it or you will piss people off big time. They are designed to work in water and are automatically activated when submerged.

406MHz ELTs do, in fact, use GPS (if available). Older 121.5 ELTs only broadcast a ping for homing. The question, however, was not asking about ELTs in the aviation sense but EPIRBs in the mountaineering sense.

No, they couldn't. EPIRB beacons have a very short range, by the time you get a signal you'd also have a signal from the beacons in for example the flight data recorder.
You seem (like a lot of people) under the impression that GPS receivers send their location to the satellite which then sends it somewhere to a data center where it can be retrieved. This is incorrect. The device only reads from the satellite network, calculating its position based on signals from the satellites. And it then uses either a short range radio transmitter or a cellphone network to transmit that location to interested parties. But of course in the middle of nowhere there are no cellphone towers and a short range radio doesn't help if the nearest recipient is far away.
On a ski slope that's no problem, as you're in civilisation and not far from help. In the middle of the ocean it's of no use whatsoever.

You may be interested to read about Distress radiobeacons. The point of the PLB system is that the location of the beacon is transmitted to a satellite network upon activation, particularly to cover situations where there is no cell phone or short range radio coverage.

@GregHewgill that's however not how the ones OP refers to work, nor how he assumes GPS works. What he assumes is that simply by being a GPS enabled device you're visible in some control room somewhere because in his mind you're sending data TO the GPS network. And that's simply not the case. Yes, there are some high end beacons that use satcom, but the typical ones used by skiers and other urbanites buying them from the local wilderness store don't, they're much too expensive.

That's not what the OP actually says though. Also, from the ResQLink page, "the ResQLink PLB quickly and accurately relays your position to a worldwide network of search and rescue satellites". An avalanche beacon is something different, which doesn't use satellite comms.

Modern EPIRBs (Emergency Position Indicating Reporting Beacons) transmit their (GPS derived) position to Search and Rescue satellites.

@DeltaLima SOME maybe, the high end models. NOT the cheap ones.

@jwenting Even if they don't transmit their positions, they will still be located by the satellites using Doppler processing. It is the whole idea behind PLBs, ELTs and EPIRBs

@DeltaLima no, without transmitting anything there's no way to locate them. If there were, you could locate a person who's just sitting there under a tree and doesn't have a device on him. You clearly have no clue how things work in the real world.

@jwenting I am not saying that transmitting is not needed, I say they don't need to transmit their position to be located. Just transmitting the distress signal on 406MHz long enough allows it to be located by satellites. Never mind, you have been provided enough links to see for yourself how the system works.

I'm not under that impression at all. The beacons I'm referring to are active 406MHz personal ELTs or lightweight GPS locators that transmit positions via Iridium, as I stated in my question. You're making a lot of assumptions, rather than following the links @DeltaLima is providing.

authors: Вадим Савенков


text:
Does every state in the US require aircraft and pilot registration?
I'm aware of both Washington and Oregon requiring, by law, registration of aircraft and pilots who are based in the state.
Is this something every state does? Do states enforce it?

In 47 years of having a pilot's license in Oregon, I have never been asked to produce my Oregon pilot's registration. I don't carry it with me, although I think you're supposed to. I do still pay the fee every registration period for the simple reason that I think supporting the state aviation department is worthwhile.

Yeah, I just moved from WA to OR and brought an airplane with me, so I'm going through the steps. Registering got me thinking that it's gotta be more common than those two states, and here we are.

MT is another state that requires it, but not all states do: KY has no state registration for pilots or aircraft. You might get a better answer on law.SE for the part about state vs. federal jurisdiction but the big picture seems to be that states can require anything they want provided it doesn't conflict with the federal regs, e.g. OR can't require you to have your license in order to actually operate an aircraft, because that would conflict with the FARs. But that's my non-lawyer understanding, so don't rely on it :-)

No registration for pilots or aircraft in Kansas either

I'm not sure on aircraft (I'm buying a part-ownership, but don't know registration details), but I do know that in the state of Wisconsin I was not required to register as a pilot. Also, in Washington pilots and mechanics don't have to register as of 2005.

@Terry - "837.030 Exhibition of certificate on demand. Every pilot operating within this state shall present a federal certificate of competency and state certificate of registration on demand. The certificate of registration shall be kept in the personal possession of the licensee when operating aircraft within this state and must be presented for inspection upon demand of any passenger, peace officer, official manager in charge of any airport, other aircraft operator or federal or state agent." Technically as a passenger in your 747 I could have asked to see your registration :)

@RonBeyer Hmm, interesting. However, though I lived in Oregon the entire time that I was flying 747s, my flights did not originate from or arrive in Oregon, so I guess I was safe. LOL Also, I'm wondering what the penalty for non-compliance would be if a captain refused to present his state registration to a passenger. If there is no penalty, there is in effect now law.

@Terry I suppose a flight technically operates within the state even if it's just in the airspace. I'm not sure what recourse I would have as a passenger other than to report you to Oregon authorities. I suppose that a peace Officer could arrest you or an airport manager may be able to keep the flight from leaving until authorities arrived.

@Terry at least for aircraft, if it hasn't been registered, it is eligible for taxation (as I read the laws), which gives them a way to penalize you, I suppose - evasion of taxes.

Do airlines really ensure all their pilots have state registration in Oregon?

No.  Nevada does not enforce any sort of registration.  At least as a practical matter: there may or may not be some law or registration, but in ~20 years as an aircraft owner (and longer as a pilot) I never heard anything from the state other than a personal property tax.

@ZachLipton No. States cannot regulate interstate commerce, per the U.S. Constitution itself. Unless both endpoints are in Oregon, the state wouldn't be allowed to make such a requirement, just as they can't require truckers to get a license for every state they drive through. Incidentally, this is also why many online retailers don't charge state sales taxes - unless the company has a physical presence in the state of the customer, the transaction constitutes interstate commerce and is not taxable by the individual states. See Quill Corp v. North Dakota.

Washington State does not, in fact, have registration for pilots (or mechanics). This has been the case since 2005. See the page you linked to in your question, or this page specifically.

No.
It varies from state to state. New York, for example, requires tax payment but no aircraft or pilot registration. New Jersey doesn't require any registration and didn't mention any taxes. In Delaware, registration is required but taxes can be waived if you register your aircraft under your corporate, instead of your own name. Iowa requires registration and so does Ohio.
I could not find a single resource which lists all states and their aircraft and pilot registration requirements. FAA does not have this information, probably because FAA does not care about state regulations.
We can create a Wiki on this topic here.

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text:
Why was my flight cancelled due to bad weather while other flights were not?
I'm stuck in Frankfurt. I missed my connection due to a delay. I was rebooked, but this new flight was also cancelled due to bad weather.
About 30 percent of all flights were cancelled today. However, if the weather is that bad, shouldn't all departures have been cancelled? Why was the weather bad for my flight, but not for other flights that actually departed?

Are all the flights going to the same place you're going?

no, it was different places but they announced the problem in Frankfurt airport, not in my destination

This is the magic that the schedulers have to execute for every flight. You can't get an airplane from B to C if either the airplane or the crew couldn't make it from A to B. And then it dominoes. Plus, if an airplane can't make it to C for whatever reason, why make it leave B?

In general, flights get cancelled when arriving flights are delayed or themselves cancelled. Your flight needs three critical things to depart on time, or at all:

an airplane,
flight + cabin crew, and
weather that meets requirements

Aircraft may not arrive due to weather diversions (couldn't land with fuel on hand, etc). If there's no airplane, your flight obviously can't depart. Same goes for bad weather at your departure airport - if it's too bad, you can't go. If the weather at your destination is bad, the flight may also be delayed because the airport can't handle as many aircraft as normal. That's fairly straightforward. Where it gets most complicated is the crew.
Crew have what are referred to as "duty and rest requirements" (at least in the US; other jurisdictions have similar rules, possibly with a different name). A flight crew is "on duty" when they're first scheduled to fly, whether the flight happens or not, and the number of "duty hours" they can have on a given day are limited. The FAA last revised these rules in 2011, as far as I know, but I'm not an airline pilot. With the 2011 rules, "Flight Duty Period limits under the new rules range from nine to 14 hours". These rules exist to prevent fatigue, a major cause of aviation accidents.
What this means is that if weather delays cause crews to overfly their limits, they may be unable to operate the outbound flight. With your example of Frankfurt, there is weather causing delays to arriving flights.
For example...
If a hypothetical crew with a 10 hour duty limit was scheduled to fly, say, three LHR-FRA round trips (call it 3 hours of flight duty time each round trip; this may not be a valid example), but were delayed on their third FRA arrival by 2 hours, they would exceed their duty limits by 1 hour on the return flight (1.5 * 2 + 1.5 * 2 + 1.5 + 2 = 9.5 + 1.5 = 11 > 10). As a result, they would not legally be able to depart.
Normally, airlines plan for this with "reserve" crews that are on call to fill in for missing, sick, overflown, or otherwise unavailable crews so that flights are not seriously delayed. When a huge storm hits, this falls apart as there are not enough reserve crews to operate all the flights, and the situation snowballs out of control.
Our hypothetical crew would be replaced by reserve pilots (and cabin crew) if they were available, and the flight might be delayed by more than the 2-hour flight delay they experienced. If not, the flight would be canceled.

ATPs, please feel free to correct any issues with this answer. I'm a lowly CFI with no direct airline experience and I'm sure there are holes or inaccuracies!

It's not just bad weather at the departure airport. Two weeks ago, I was flying from Frankfurt to Brussels and we were parked near the runway waiting for departure clearance for longer than the actual flight time! The reason was that due to unfavorable winds in Brussels only about half of the runways that are normally used were available, so we weren't allowed to take off until we had a confirmed landing slot in Brussels. Note that "half the runways can be used" pretty much means "half the flights need to be canceled". Even if it had been the most beautiful weather in FRA, we wouldn't …

… have been allowed to take off due to "bad weather".

@JörgWMittag - that's a fair point. I've certainly had flights delayed (though not canceled) due to flow control in the past.

Also, in bad weather minimum separation between aircraft can be increased and that too decreases capacity. Or in snowfall having a runway closed every so often for the runway to be cleared of snow very obviously decreases capacity.

@Notts90 Surely it's the passengers', not the airline's, responsibility for the passengers to show up at the airport? The only significant exception to this that I can think of is if it's a connection flight, in which case either the departing flight will wait (if it is a short delay) or the passengers involved will be rebooked onto a later flight (if it is a significant delay).

@egid Also, not all aircraft are equipped equally, or handle equally in bad weather. I don't know about those that frequent Frankfurt, but I don't think it's impossible for certain types of weather to impact certain types of aircraft more than others. I can definitely see potential here for a difference between e.g. turboprops and jets. That could result in weather forcing grounding of only some types of aircraft, which would impact a portion of the flights, while others are able to make it out (or in, as the case may be).

@Notts90 Probably not. The reason is that plane will fly different passengers once it reaches its destination. That's why cancellations have a ripple effect. I'm willing to best it would cost the airline more money to leave an empty airplane where it is, than to fly it empty to the destination. Easier to juggle one set of passengers than two.

@gsnedders If the weather at your destination is bad, the flight may also be delayed because the airport can't handle as many aircraft as normal. - I'm trying to write this answer for laypeople, not aviation folks. There are any number of reasons an airport could have a reduced capacity for arriving or departing flights. :)

@gsnedders If the bad weather includes snow/ice conditions the available de-icing equipment and personnel to operate them may pose an upper limit on the maximum # of planes that can be prepared for departure. And small planes are in general quicker to de-ice than big ones. If de-icing capacity is low they may prefer to cancel some bigger birds to make room for servicing more smaller planes.

If the bad weather is a hurricane or large thunderstorm cell right over the airport, yes you would expect all flights to be cancelled rather than just some. But if the weather brings low visibility, like parts of Europe have experienced this week, it is a slightly different story. The main reason for cancellations is that the airport cannot operate at full capacity.
Usually, aircraft can takeoff in very low visibility (such as fog), but to land the visibility requirements are higher. So if your aircraft is already on the ground before the bad weather hits, it still might be able to leave, whereas another flight is cancelled because the aircraft operating it can't land.
However big airports with frequent visibility problems usually have a category 3 ILS (Instrument Landing System). This category allows an appropriately certified aircraft and crew to land in virtually zero visibility using Autoland. But this system has limitations. The ground-based transmitters are sensitive and need large protected zones - this means that certain runways and taxiways cannot be used at the same time as an Autoland.
This ties in to Low Visibility Procedures (LVPs). Every airport and airline has their own, but the common theme is that everything slows down. The cumulative effect of both Autoland operations and LVPs is that the amount of movements an airport can safely handle per hour drops dramatically.
You can imagine that if there are 50 scheduled flights per hour, but weather reduces capacity to 30 per hour, 20 flights will spill over into the next one. You'll then have 70 flights fighting to use 30 slots, then 110, and so on as the day progresses. For busy airports, mass cancellations are the only way to get things back on track - but 30 flights per hour can still go ahead. In reality the airlines will be told to cancel a certain number of flights and yours might be one of the unlucky ones picked.
Another thing tor remember is that the bad weather in question might not be at the airport you are at, but rather the destination or en-route. Rather than being stuck in a holding pattern for a few hours waiting for the destination airport to clear, it is preferable to wait on the ground - so even if the weather is sunny at the originating airport, a flight could be delayed or cancelled due to weather at the destination.

Autoland, not autotaxi... as a pilot, you still need to be able to safely get your aircraft off the runway, and ideally to a gate.

@MichaelKjörling yes there is no such thing as autotaxi. A category 3C ILS allows for landing in no visibility whatsoever, but because a little bit of visibility is needed for taxi, no airport has bothered with this certification yet

As @Ben correctly guessed, Frankfurt airport was (and still currently is) reduced in capacity due to snowfall. I heard about it yesterday and this news article had more details (translation below):

Zwischenzeitlich stand an Deutschlands größtem Luftfahrt-Drehkreuz nur eine Piste für startende und landende Jets zur Verfügung. Eine Sprecherin des Flughafenbetreibers Fraport bezeichnete die Situation als «dramatisch». Selbst auf den geräumten und gestreuten Bahnen seien wegen des anhaltenden Schneefalls nicht die vorgeschriebenen Bremswerte erreicht worden.

Translation:

Temporarily, Germany's largest hub airport only had one runway available for starting and landing jets. A spokeswoman for airport operator Fraport called the situation "dramatic." Even the ploughed and gritted runways did not reach the required deceleration values because of the continuing snowfall.

This might have been a major reason that a major part but not all flights were canceled.

Welcome to av.se - nice answer!

"Not reach the required deceleration values" - i.e. due to the icing, planes braked slower and would need more runway length. This would explain why some (heavier) planes would be unable to land while others could still operate.

If an airport is running at reduced capacity due to bad weather (or a closed runway etc), then airlines will generally cancel short-haul fights first.
After all, Frankfurt -> Munich is almost as quick by train as by air. Frankfurt->Paris isn't hard by rail. Frankfurt->London is doable for the return leg (takes about 15 hours). But Frankfurt->New York? Forget it.

Another requirement for flights is weather minimums at the destination airport. If the destination airport is forecast to have within +/- 1 hour of ETA ceiling and visibility less than 2,000 ft or 3 sm visibility, than a suitable alternate airport with certain weather criteria are needed.
Therefore airplane "A" can not leave because the weather at the destination is too bad or an alternate is not cost effective to divert to if needed. At the same airport, other airplanes are coming and going and airplane "B" will leave because it is headed towards good weather.
This is often the case for long international flights. Say you are planing a 12hr flight from Frankfurt to New York City, USA. If the weather is bad for 500mi around NY, the air carrier may not want to risk being stranded some where else. If the weather is expected to worsen, a lot of bad things can happen during the 12hr flight. But other closer flights, or flights to other areas of the USA my be landing and taking off.
Also two carriers with the same departure and destination airport may have a different risk assessment. One carrier may have attractive alternate flights with good connections later and choose to take the risk. The other carrier may not have good options. Therefore one will be willing to depart and the other will delay "due to weather".

If a plane is scheduled to fly from A to B to C to D, and it does not appear that weather at B is going to be suitable for flying any time before the plane is scheduled to arrive at C, would it be possible for the airline to fly to C (skipping B entirely) and either have passengers who were going to B either disembark before taking off for C, or else fly such passengers to C and then book them on a flight from C to B?  Do airlines ever do that?

Additionally to all the other answers, there is one factor that could also explain a difference of treatment between two different flights: the capabilities of the aircraft.
Some aircraft are better equipped than others to face bad weather conditions. It depends mainly on their equipment, size and design.

Welcome to aviation.SE!

smaller aircraft are more fragile - is that actually true? I mean, aerobatic aircraft are quite small compared to a 777, but they seem quite robust! :)

To be fair, you have to compare all things equal otherwise, you can’t compare aerobatic aircrafts with commercial aircrafts :)

Okay, so, what are you suggesting we compare? Is there anything that actually suggests that a smaller aircraft is more fragile? What I understand about the challenges engineering large aircraft, the opposite could be true.

Whatever. I’m removing that detail that seems to get all your attention.

Another reason capacity can go down, one that's given me some close calls:  The rules for how far apart aircraft must be is higher when they can't see each other.  Take two runways a bit too close together at a busy airport, add fog.  Oops, while both runways are usable the airspace can only handle one runway worth of planes.  Half the flights get delayed/cancelled due to weather even though the airport is still open.  The trip to visit her family used to connect through an airport notorious for this problem.

"The trip to visit her family"? Whose family?

@FabioTurati "Her" = my wife.  Don't be fooled by my name, I'm male.

Ok, but that's not the point. The point is that you talk about "her family", but you never mention who she is. To make it understandable you should [edit] that sentence to "The trip to visit my wife's family".

@FabioTurati I would think most people would assume that an unspecified "her" that I was traveling with would be a wife or significant other.

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text:
Why do some aircraft have multiple ailerons per wing?
In a recent flight on an Airbus A380 I noticed that its ailerons are split into three segments which move independently.
What advantages does this design have? Do other aircraft have split ailerons (or other control surfaces)?

related question for what  is called split rudder

To force us to use 2 more  costly metal gear servos :P

@Iceman: humph! A cost containment engineer would immediately change out those expensive metal gears for less-expensive-but-still-perfectly-serviceable plastic gearing, at a fraction of the cost. THAT would then require a liability-and-plausible deniability engineer to get together with a political contributions engineer to ensure that laws were changed so that the manufacturer could not be found to be at fault in case of a crash due to the failure of the plastic gears. Don't worry - be happy! :-)

General Reasons
There are three main reasons for having multiple ailerons per wing on large aircraft:
Aileron Reversal
On a large aircraft, at high speeds a deflected aileron can twist the wing enough to cause a net roll torque opposite to the one intended.  The further out on the wing an aileron is, the more likely this problem is to arise.  For high-speed aircraft, this necessitates an outboard/inboard aileron, with the outboard being locked out at a certain speed limit. On the Airbus A380, the downwards motion of the outward aileron is locked out at 240 KIAS, and upward motion at 300 KIAS.
Systems Redundancy
Another issue is that on most large aircraft, it is simply infeasible to have cables running through the aircraft, so hydraulic systems are used instead. Having ailerons split would allow for more redundancy of system failures, allowing more controllability in these failure conditions.
Load Alleviation Function
Building on what Bret Copeland has already discussed in his answer, multiple ailerons can be used by fly-by-wire computers to flex the aircraft's wings in a specific manner to allow for less loading on the wing during cruise (counteracts the wing's natural tendency to flex upwards), as well as allowing for dynamic turbulence alleviation.
One of the examples of using this is in Airbus's Safety First magazine (July 2012), where they use the flexibility of having three ailerons to tune out lateral accelerations in the rear of the aircraft changing the gains of each of the controls. By being able to move the centre aileron a fraction after the inner aileron, they managed to avoid these initial shifts during flight testing of the A380.

Other Aircraft
The majority of airliners have multiple ailerons, however in some instances (such as the Airbus A310), there is no outboard aileron -- this function is replaced by spoilers.
Another example of using computers on multiple ailerons is the Boeing 747-8, with the use of the outboard aileron to fix issues relating to the development of flutter in certain extremes of the flight envelope, called the Outboard Aileron Modal Suppression (OAMS) system.

Good answer.  But one sentence seems incorrect: "Another issue is that on most large aircraft, it is simply infeasible to have cables running through the aircraft, requiring the use of hydraulics."  Can you clarify that or correct it?

Isn't "aileron reversal" better described as the aileron forcing the wing to twist in a way that reverses the aileron's intended effect-- not the material of the aileron itself twisting?

Another factor could be that smaller actuators could be cheaper than inventing new super powerful ones that could move a gigantic single aileron.
It could also be limited by the wing thickness, you can't build the actuator big enough to fit into the wing and at the same time actuate the entire surface.
Plus the ailerons would need to be a lot stiffer if they were actuated by one actuator. So this is probably the light weight cheap solution.

I don't know the specific rationale in this case, but if you think about mechanical advantage, the farther an aileron is out from the center of gravity, the more roll effect will have on the airplane. You'll notice in the image that the outer aileron is deflected less than the inner aileron, even though they are probably producing roughly the same roll moment.
A benefit I see is that it undoubtedly reduces wing-loading at the far end of the wings, and therefore reduces stress/flex on the wing during turns. This could be very important for an aircraft as massive and heavy as an A380, but less important for smaller aircraft where the wing-load is naturally less.

In case of the A380 I've read in the FCOM that they don't deflect all ailerons at the same time for passenger comfort and the ailerons are used to dampen out wing oscillations e.g. caused by turbulence.
The A330 has a split aileron as well.

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text:
Why were flying boats phased out?
Before  WWII, flying boats were a popular form of transport, and the advantages are many: No need to build runways, capability of emergency landing on water, availability of large landing sites and no tire wear and tear. Why have they been abandoned?

Even flying boat can't land on water with any significant waves. So there is not much use for emergency landing.

The biggest single reason for the decline of flying boats was the proliferation of long runways during World War II. The infrastructure advantage of flying boats – the ability to operate heavy aircraft without long runways – was no longer relevant. Large airfields were a result of the long-range heavy bomber campaigns in Europe and Asia.
Century of Flight has an interesting article that goes a bit more in depth.

Alhtough the initial prerequisite for the substitution was the development of aircraft which had sufficient range and reliability to get rid of seaborne fueling stops.

That's true, but I'd argue that the earlier long-range aircraft had pretty abysmal takeoff performance. They needed the space available on the water to reach the ranges they offered. During WWII, much more powerful engines were developed that allowed the DC-6 and Constellation to have both great range and shorter takeoff requirements, plus the runways were now much longer.

Apart logistics and the availability of long runways afterr WWII, the reason for the phasing out of the sea planes was maintenance. The aircraft was operating in an extremely corrosive environment, something that can be seen nowadays in the firefighting planes like the Canadair and other smaller seaplanes. More info: FAA Corrosion Control.
Also the engines need to be inspected and cleaned after every operation. Generally speaking, operation in corrosive environments like water is something that requires very careful inspection and time consuming maintenance. For example even the Chinook helicopter needs extensive cleaning after operations that involve landing on water.
Finally the increased drag due to the shape of the flying boat is something that every designer and airliner wants to avoid.

also, the mass of a flying boat fuselage is considerably higher than that of a landplane, eating into payload.

Flying boats were a solution for long over water flights when engines were less reliable and could not produce sufficient power to lift large loads.
Regular flying boat services between New Zealand and Australia which I am most familiar with, often never flew above 5,000ft. This meant they subjected passengers to considerable discomfort at the mercy of bad weather.
In areas where there were primitive support facilities and no runways, especially in the Pacific, these flying boats continued to operate into the early 'sixties, but as more and more runways were built the need for flying boats diminished and the cost increased.
Tahiti and New Zealand operated the last scheduled routes for large flying boats in the Pacific.
Shin Meiwa in Japan did propose a civil version of their impressive STOL US-1 which would have carried >50 passengers in a pressurised cabin. India is interested in such aircraft for search and rescue but no orders have arisen for the civilian aircraft.

Beriev in Russia has also developed an equally impressive Be-200 jet powered flying boat (smaller sibling of the A-40 Albatross). The Be-200 is offered as an amphibious airliner configuration, but so far airlines have not shown any interest.

Great post, lists the major reasons and has pretty pictures of the best flying boats with their state-of-the-art hulls. I would add only one thing: The weight penalty of a flying boat hull is considerable, and it reduces the possible payload. So it is simply less profitable to run an airline service using flying boats.

Thanks Peter, Germany had some amazing flying boats worthy of note like the BV222 Wiking and of course operated services to Rio de Janiro before the War. One cannot beat flying boats for romance and excitement.

The second biggest reason:  Where would they land in Denver?  And many more cities that have robust air traffic but not many lakes or waterways that are suitable.

Well, most flying boats actually have wheels and can land on a normal runway.  :)

@Lnafziger technically those are amphibians. And at the time (early 1930s) most were straight flying boats. Even the PBY Catalina wasn't an amphib until the final few models late in its career.


text:
Do I have to do all exercises during a checkride, even if I did them in a previous one?
I am currently a private pilot with an instrument rating and multi-engine rating.  I own and regularly fly my own twin engine airplane and have been thinking about getting my commercial rating.  Part of the PTS requirements for the commercial multi-engine include the emergency procedures for engine out/emergency descents, etc.
Since I have already had a check ride (multi-engine rating) that included ALL of these maneuvers, do I still have to perform these on a commercial multi-engine check ride?

Yes, if this is your initial rating on a Commercial certificate, you have to do all of that rating's required tasks. A checkride for a given certificate is always self-contained. In the case of an additional Commercial rating (ASEL, for example) you can refer to the appropriate "Additional Rating Task Table" and you'll see that some areas are already covered by the existing Commercial rating.
If you look closely, you'll notice that the PTS standards for the same maneuvers are more precise for Commercial than they are for Private. Notice that Steep Turns differ in both bank angle and execution technique:
Commercial (from FAA-S-8081-12C)

Task A: Steep Turns (AMEL and AMES)
References: FAA-H-8083-3; POH/AFM.
Objective: To determine that the applicant:

Exhibits satisfactory knowledge of the elements related to steep turns.
Establishes the manufacturer’s recommended airspeed or if one is not stated, a safe airspeed not to exceed VA.
Rolls into a coordinated 360° steep turn with at least a 50° bank, followed by a 360° steep turn in the opposite direction.
Divides attention between airplane control and orientation.
Maintains the entry altitude, ±100 feet, airspeed, ±10 knots,
  bank, ±5°; and rolls out on the entry heading, ±10°.

Private (from FAA-S-8081-14B)

Task A: Steep Turns (AMEL and AMES)
References: FAA-H-8083-3; POH/AFM.
Objective: To determine that the applicant:

Exhibits satisfactory knowledge of the elements related to steep turns.
Establishes the manufacturer’s recommended airspeed or if one is not stated, a safe airspeed not to exceed VA.
Rolls into a coordinated 360° turn; maintains a 45° bank.
Performs the task in the opposite direction, as specified by
  the examiner.
Divides attention between airplane control and orientation.
Maintains the entry altitude, ±100 feet, airspeed, ±10 knots,
  bank, ±5°; and rolls out on the entry heading, ±10°.

The more precise standards was the main point that I was going to highlight as well!


text:
How does a pilot replace their logbook if it has been lost?
I got my private pilot license when I was 17 but was unable to continue flying. I am moving into a position to get back in the air, but I no longer have my log book as it was lost between moves. What is the best way to move forward?

To move forward with what? Why specifically do you want to prove how many hours you have? Do you actually have a pilot's license?

I assume so - "I got my private pilot license when I was 17"

@egid Yes, I guess my main point was to clarify if he just wants to restart flying (in which case an 8710 would be fine) or if he's trying to get a specific rating or even job where he needs to prove a certain number of hours cross-country or in type or whatever.

@Pondlife I just want to restart recreational flying and possibly pursue additional ratings.

The best approach is to start a new logbook with totals that carry over from your latest FAA 8710 - in this case, it sounds like you will roll back to the hours from when you earned your private pilot certificate. There are some other options listed in FAA Order 8900.1, 5-172, but it's unlikely any of them will work for your situation (except, perhaps for "Receipts for aircraft rentals", if your FBO is still open and still has the records).
You can request a copy of your 8710 from the FAA, which I'm gonna quote here because that's the best way to not screw anything up:

Airmen who have lost their logbooks or flight records may request copies of their files from the FAA [by sending this form] to the following:

FAA Airmen Certification Branch, AFS-760
P.O. Box 25082
Oklahoma City, OK 73125

or

FAA Aeromedical Certification
P.O. Box 25082
Oklahoma City, OK 73125

Once you receive the copy, the first line in your new logbook should probably summarize all the totals from the 8710 (just like if it was a flight). The remarks would specify "time forward from 8710 dated DD/MM/YYY" or something to that effect.
Best of luck getting your records back!

What is on an 8710 for a GA pilot?  Reading the description is sounds like it is just your various pilot certificates and ratings.  Would there even be times?

@JerryKur, an 8710 is an 8710, whether you're GA or not. There are fields for flight experience, only some of which would be required for a PPSEL, for example, but they're definitely there. My 8710 includes 0.5 Helicopter, for example, just 'cause it was in my logbook.

So how did these entry like your 0.5 of helicopter get to the FAA to put on your records?  I have never sent anything to the FAA unless it is for a rating or medical?

When you fill out an 8710 for a rating, you can put any time on it that's in your logbook, even if it's in excess of the requirements for that rating. I had 0.5 helicopter in my logbook when I was applying for some advanced rating, so onto the form it went.

Thanks.  This is a very interesting thread.  I guess I better not lose my log books because it has been several of them since I added my last rating.

I've just had my Airmen's Records provided from an 8710 request, but they only seem to have my medicals, nothing from my Instrument rating. So the total hours will be that listed on the last medical you got, not from any other training.

As you wrote: "I just want to restart recreational flying and possibly pursue additional ratings", you don't technically need your old log book to start flying again if you still have your license.
See the answers on this question.
You'll need your license, a current medical, and a BFR.But I don't think you need proof of hours.   Of course, getting a fully signed off BFR is a lot easier if you have a log book showing recent time, but it is not required.

Just to point out... he's specifically asking what to do about his logbook, not what he needs to start flying again! Your answer is correct, but maybe is better as a comment on the question?

And, he doesn't technically need his logbook - but if he ever wants a subsequent rating, he does need his total times, and an 8710 that's missing those hours required for Private will probably raise some eyebrows.


text:
How common are conformal fuel tanks?
I know that the F-16 (F-16I and Block 50/52/60 models) have conformal fuel tanks standard now on top of the wing/fuselage area.  The Silent Eagle model of the F-15E proposed by Boeing for South Korea, and other F-15E customers had them added.  The F-18E (Superhornet) has demoed a set recently.
But on older aircraft, how common were conformal fuel tanks?  Or have they always been drop tanks before?

The conformal fuel tanks of the F-18 are for the next gen model, the "super duper" hornet.  Along with conformal fuel tanks it has larger engines, internal stores, and some other tweaks.

Technically speaking, conformal tanks don't take up hardpoints, so I'm not sure what we have today has an equivalent in older designs.
Otherwise, I'd say somewhat common; streamlined fuel tanks and other conformal packages have been used for quite a while in several different designs.
Some World War II Supermarine Spitfires used what was called a "slipper tank" - a streamlined package of up to 90 gallons (additional source).
The early 1960s-era English Electric Lightning used a 'conformal ventral store' that could hold either a fuel tank or rocket engine (?!). The Gloster Javelin used a similar set of "bosom tanks".

Hardpoints were a concern on older designs, primarily smaller fighter-bombers. The P-51, for instance, could carry droptanks on its wing hardpoints when flying bomber escorts, or bombs for precision strike missions or CAS. The P-51 had the ability to fit a slipper tank as well if greater range or loiter time were needed and the hardpoints were unavailable.

I've never seen a P-51 slipper tank, got a link? How did it fit with the gear and radiator all converging right there?

IIRC the tanks actually fitted over the top of the fuselage like saddlebags behind the cockpit. But, I can't find a picture online. By the time the D variant was introduced the plane could carry a lot of gas without any special modification (like 480 gals with standard droptanks, which given the cleaner piston-engine design was plenty)

Hm, never seen that. If you ever find a link share it! I've only seen the ridiculous huge ferry tanks that look like floats.

The Messerschmitt Bf-110 used a conformal fuel tank under the forward fuselage, colloquially known as "Dackelbauch" (Dachshund belly). The picture below should explain well why this name was chosen.

They were introduced to allow planes stationed in Norway to attack targets in Northern England. When empty, their content would be a dangerous mixture of air and fuel vapor, so they were not very popular with their crews and only used briefly.
If you want, you could even call the center wing tank of some biplanes a conformal tank. However, conformal tanks are rather unusual.

If a center wing tank counts, wouldn't a normal wing tank? :)

They're not unheard of, as from your examples. Like any design, they have advantages and disadvantages.
Pros:

Typically more aerodynamic, and lighter, than a droptank of similar capacity.
Carried closer to the fuselage than hardpoint droptanks, reducing roll moment, increasing maneuverability.
Doesn't take up hardpoints desired for munitions (the primary reason the F-15E uses them is that it wouldn't have a useful range carrying 2000lb Mk-82s otherwise)
Typically allows more fuel storage than the centerline droptank (the only other location that isn't usually a munitions hardpoint)

Cons:

Aerodynamics are still negatively impacted
Cannot be jettisoned mid-flight for weight/drag advantage
When empty of liquid fuel, CFTs can still contain a combustible vapor which could explode given a hit that might otherwise do only superficial damage (most modern designs use a bladder to contain the fuel and minimize vapor release into the CFT shell)
Not all airframes tolerate CFTs of a meaningful size without significant changes in handling. The F-16I's performance is apparently unaffected by the additional 460 gallon-capacity CFTs, but the F-15E/I/SK, despite the airframe's air-superiority pedigree, is known to be at a disadvantage in a dogfight to the F-15C, the USAF's primary air-superiority variant.


text:
How to reduce altitude in a passenger jet without gaining forward speed in an emergency?
Assume the pilot is flying too fast and high for an emergency landing. What movement of the control surfaces must they apply to land the aircraft safely on the runway? I heard this type of manuever is also used in gliders and light aircraft

You may want to read the story of "the Gimli glider", where this situation occurred.

It's called a sideslip. Cross rudder and aileron controls and let the fuselage drag take care of the rest.

Ah that's a good question indeed. You asked

How to reduce altitude in a passenger jet

Normally most of the passenger jets have spoilers They are effective and can be deployed at any speed.
Now what happens in case you don't have spoilers for any reason. I was discussing the subject with a pilot many years ago and he told me the trick you mentioned: you apply rudder to one direction (I assume opposite to the engine rotation to avoid unpleasant surprises). That increases dramatically the forward surface of the plane against the relative air flow. That results in increased drag and thus speed loss.
But yaw causes roll (and vice versa). Also the wing of the side you are yawing to, has less lift because it is shaded from the forebody of the plane. This is where the aileron is needed. You need aileron to maintain lateral stability and prevent the aircraft from rolling. See the image bellow. The orange lines denote the area of increased drag by the fuselage. The green area is the "shaded" area of decreased lift of the wing.

Top view from wikipedia. Derivative work by me.
According to that pilot, this is more effective than spoilers. But there is a trap: You need to be careful not to yaw the plane too much because the shaded wing will loose too much of its lift and will result in capsizing the plane.
EDIT: Finally, you mentioned emergency. There are different types of emergencies. Pressurization is an emergency situation but does not affect aircraft control (at least not directly). Hydraulics problems or engine loss is an emergency as well. But that will affect the way you will handle the aircraft. Here I cannot help you. A trained pilot perhaps can answer, though I believe that the answers will vary depending on each planes flight manual.

In addition to the standard aerodynamic controls - ailerons, rudder, elevator - many large aircraft also have a spoiler (also known as speed brake). This has the effect of adding drag without adding lift - in fact in some designs it will reduce lift. This allows a swift descent to be made without increasing airspeed. Gliders also have spoilers, as they only have one shot at a landing.
In the absence of a spoiler (or in addition to it) an aircraft can dump lift without increasing airspeed by carrying out a manouevre called a "forward slip". The ailerons are applied in one direction and the rudder in the opposite direction, meaning that the aircraft is actually moving at an angle to the direction the nose is pointing (see the answer by Stelios for a nice diagram). This adds drag and disrupts the aerodynamics of the wings.  This was among the manouevres used in successfully landing the Gimli Glider.
In either case, just as in regular flight, forward speed and vertical speed can be manipulated together by using the elevator: lowering the nose increases both airspeed and descent rate.

Just wanted to point out that in a slip, speed and descent rate are manipulated by elevator.

Two things, one, you may want to use "forward slip" to differentiate from a regular slip (part of an uncoordinated turn).  And here's a genuine emergency that used that particular maneuver that you might consider including: https://en.wikipedia.org/wiki/Gimli_Glider


text:
Why is it hard to see G1000 with sunglasses?
I got checked out in the G1000 172 at my flight school just so I could schedule to fly when the two steam gauge 172s were booked. I'm very impressed by the G1000, but I can't wear sunglasses when I fly the NAVIII. This is with the avionics dial on the lighting panel turned all the way up.
Does anyone else have this problem? Is it my sunglasses?

Are they polarized?

They are indeed

The FAA is on record as being against polarized sunglasses. See page 5 of the following publication: https://www.faa.gov/pilots/safety/pilotsafetybrochures/media/sunglasses.pdf, which I should have read but didn't and now have a pair of sunglasses that are useless for glass cockpits.

Related  question

The screens are LCDs, which have a polarized filter layer over them. That layer is usually placed at a 45° so they are misaligned with your polarized sunglasses which are aligned vertically. You can confirm this is the problem by turning your sunglasses at different angles and see if the screen changes.

Bingo! Can't wait to test this out.

The polarization on the sunglasses is probably the issue. It's not a good idea to fly with polarized sunglasses on anyway. It can reduce the glare off an airplane when that glare might be the queue that saves your life.

This is 100% what's up. I modified this answer to be a little more certain about things.

Gratuitous extra info: A polarization filter is a key part of an LCD. Liquid crystal itself can only change the polarization of the light going through it; it's the polarization filter that then blocks some of the light making pixels appear light or dark : https://en.wikipedia.org/wiki/Liquid-crystal_display#Overview

However, it would be easy to "de-polarize" the light coming from an LCD, so you could still read it at any angle. A plastic foil of a cigarette packet mounted on a display at the correct angle works well enough to demonstrate the effect. I don't understand why manufacturers don't spend a few cents for such a  foil (of course, higher quality than the foil from a cigarette pack...)

@RyanBurnette: Ahem "cue" ;)

I read a few other sources that say flying with polarized glasses is fine. In the end we'll all make our own choice about it.

@DavidRicherby: Planes are made of metal, but usually are painted, too. The paint generates polarized glare. About the LCD: Of course, polarization is the principle of work inside an LCD. But you can convert the linear polarized light coming from the display into circular polarized light, which is not affected by polarizing sunglasses. As said, a simple foil on top of the display is enough. My opinion: The blue of the sky is also partially polarized and so shaded by glasses. Clouds and other objects stay bright and are better visible, which is a clear pro for polarized glasses.

@sweber I was under the impression that the thin layer of paint wouldn't cause polarization but it seems I was mistaken.

@DavidRicherby, it is not the paint that causes polarization. Whenever light is reflected from a surface at an angle (not perpendicular), it is polarized.

@sweber: Polarized sunglasses are polarized so that they filter out reflections, mainly from horizontal surfaces. Most of the time that is what you want, but not when looking for other aircraft.

@JanHudec Sure, it's not paint that causes polarization per se. Rather, metals cause non-polarization and I was under the mistaken impression that painted metal had enough of the properties of metal that it would also cause non-polarization.

Thanks guys. Did not know what the polarization filter did in lcd's, just knew there was one. You learn something new every day. Edited answer to reflect.

@DavidRicherby, yes, metals don't cause polarization on reflection, but once the paint is opaque (and that's it's point) it is the paint and not the metal that reflects the light, so the reflection becomes polarized (I wonder what a metalic paint does though).

First off, metallic paints actually don't have any metal (there are some paints with high metal content to make them conductive for electronic shielding, but they're not very pretty). Metallic silver paint is just a specific shade of grey in a gloss base with mica particles suspended in it to provide that metallic glitter. So on a plane painted silver, the reflection is 100% paint. The mica flakes can cause a scatter effect on polarization because they're oriented at different angles, but it's minor compared to the reflection off the high-gloss surface.


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What does the instruction "Climb heading [BEARING] to [NAVAID] 2.5 DME" mean?
I am examining FAA's Standard Instrument Departure Procedures (SIDs) and while reading their textual description, I came across this instruction from
LGA's La Guardia Five Departure SID, for Runway 13 (Whitestone climb): "Climb right turn heading 180 degrees to LGA 2.5 DME then left turn heading 040 degrees etc."
Could someone explain to me what the phrase "heading to LGA 2.5 DME" means? Does it mean that the pilot maintains this magnetic bearing (180 degrees) until the distance between the aircraft and the LGA (NavAid) becomes 2.5 nautical miles?

Is the "4.5 nautical miles" at the end of the question a typo?

Yes indeed, thanks for pointing this out!

DME is "Distance Measuring Equipment". It tells you how far you are from the equipment transmitting the signal. This is often co-located with a VOR, or at an airport.

turn heading 180 degrees to LGA 2.5 DME

So, this means turn due south and continue until you are 2.5 nautical miles from LGA. At this point you're instructed to turn left on to a heading of 040.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
How is drone (UAS) traffic regulated in the US?
Does the FAA regulate drones at this time?
Maybe they regulate only a certain class / size of UAV / UAS?
Is drone regulation to the level that traffic is managed through ATC?

You also want to be aware of your local restrictions. For example, we got shut down in Carson, CA. Also try to add more context as certain uses of drones carry varying level of regulation not just by the FAA.

Small note, Drone is an incorrect term for a UAV or UAS, spun into popularity by the media. Drone is a military term, meaning something you shoot down (ie, My UAV is attacking this drone).

Regulations regarding UAVs are very restrictive in controlled airspace. Whenever a company wants to test out a UAS, they have to request a block of airspace from the FAA (or local ATC body). This block is restricted to UAS traffic. No manned aircraft are allowed in that area for the duration of the test.
Currently companies are working with the FAA to integrate UAVs into the regular airspace system. Recently, the FAA designated 6 states as test sites for the FAA to test UAVs.

As of yet, I cannot tell if drone traffic is regulated, but I do find that the FAA has created a committee to design the appropriate architecture and guidelines.

According to the FAA Modernization and Reform Act of 2012 as (1) the aircraft is flown strictly for hobby or recreational use; (2) the aircraft is operated in accordance with a community-based set of safety guidelines and within the programming of a nationwide community-based organization; (3) the aircraft is limited to not more than 55 pounds unless otherwise certified through a design, construction, inspection, flight test, and operational safety program administered by a community-based organization; (4) the aircraft is operated in a manner that does not interfere with and gives way to any manned aircraft; (5) when flown within 5 miles of an airport, the operator of the aircraft provides the airport operator and the airport air traffic control tower…with prior notice of the operation; and (6) the aircraft is flown within visual line sight of the operator.
http://www.faa.gov/uas/publications/model_aircraft_operators/
FAA has released a set of "Dos" & "Don'ts" related to flying UAVs(drones):
http://www.faa.gov/uas/publications/model_aircraft_operators/assets/media/model-aircraft-infographic.pdf
The Regulations and Policies pertaining to the use of UAVs(Drones) in US airspace is available on the FAA website
http://www.faa.gov/uas/regulations_policies/


text:
Are there standard ground-tether systems for unpowered aircraft?
Do grounding systems have any standards or conventions?  Is tethering specified in any way?
I can understand the engineering aspects of the question, but I am wondering about regulation or convention.
.....I have a suspicion that any kind of formal or experimental craft / flyer is probably not regulated, so long as it doesn't 'escape' and remain in the air while it drifts into a controlled airspace.

I've participated in many balloon flights, and have never seen anything specific with this, so I suspect the answer is too simple ('no') or that this question is otherwise not well formatted
this question may be too close to the history of experimental-craft
I would appreciate help with proposing tags for this question

Would it even qualify as an aircraft if still tethered? Sounds like you're describing a kite. :)

I am mostly thinking about balloon-craft — but I am also thinking about kites and other tethers systems that incorporate glider / wing / sail.

Not sure if it qualifies as an "aircraft", but I know in the US the FAA regulates tethered balloons and such, so I'll post an answer in that vein. Maybe the answer will help you with tagging ideas...

In the United States moored balloons (or kites) are governed under Part 101 of the FARs (a much neglected and very short corner of the regulations that also covers amateur rocketry and "unmanned free balloons" -- looking at your profile it's probably a section you'd find very interesting!).
In this particular case you're probably looking for Subpart B - Moored Balloons and Kites.

The FAA is mum on the specific engineering requirements of mooring systems - I expect they anticipate you will work with structural and mechanical engineers to design a tethering system that can safely hold the loads your moored object will place on it (or just tie it to the biggest, most structurally secure thing you can find, with a nice heavy rope and a proper knot).
There are a few things they ARE pretty specific about though.

Some operating limitations (altitude, size, location, visibility).
The fact that you have to tell them about it in advance
(At least if it's more than 150 feet AGL, per 14CFR101.15)
Lighting and marking requirements for the tether(s)
(14CFR101.17, which basically says the mooring line must have pennants (daytime) and/or lights (nighttime) to ensure visibility)
What happens to Balloons if the tether breaks
(14CFR101.19, which basically says if the balloon breaks free of its moorings you need a "rapid deflation device" that gets it down in a hurry so it's not just wandering around up there).

Interestingly they don't seem to care so much if a kite escapes its moorings.

Really great sussing that out, particularly FAR pt. 101 .

@TheWhiteDiamond Its a section I'm pretty familiar with because I used to coordinate rocket launches.

If kite breaks loose, drag quickly accelerates it to wind speed, but then it's not producing any lift and quickly falls to the ground. So they don't need to care, because kite is not flying anywhere for simple physical reasons. (And if you fly it so close to something that it falls on it and damages it, you are liable from civil law anyway and additional regulation is not needed.)

@JanHudec "not flying anywhere" is a pretty relative statement: I've seen kites break loose from strings gain quite a bit of altitude (and travel a substantial distance) before they come back down. I could easily see one flying in a park near an airport winding up in the approach/departure path on a breezy day, it's just likely to not stay there very long for the reasons you describe. (In other words this is more airspace management by the "Big Sky Theory" - it's unlikely to collide so it gets ignored.)

Tethering for balloons is largely left up to the manufacturer.  Most have specific requirements / recommendations in the aircraft manual.
Most pilots and manufacturers will recommend a 'three-point' tie-off system.  This system connects three ropes from the top of the balloon to the up-rights on the basket and then attaches a secondary rope to each of those which is tied to a car or truck.  This provides a stable tethering system that 'holds' the envelope in place is very robust.
Manufactures normally also allow three ropes to be connected to the uprights only but if it gets windy this can be very hard on the system. I looked around for the PDF version of my manual but am having a hard time finding it; its even got illustrations.


text:
Why fluids are forbidden in flights, while nitrate- and peroxide compounds aren't?
As I know, passangers on most international airports aren't allowed to take any fluid with them into the deck.
But, for example, I can't remember for any deeper examination for nitrate- or peroxide compounds. Although they had been much dangerous, as a glass of water.
Why is it so?

First of all, your statement, that it's not allowed to bring any liquid (gels, spray cans, ...) with you on most airports is simply not true.
In the EU, any liquid must be in containers of not more volume than 100ml, and all containers must be in a transparent, close-able plastic bag of not more than 1000ml.
In the US, the rule is the same, but the limits are a bit lower for smoother numbers, like 3 fluid ounces (~90ml) and 30 fluid ounces (~900ml). (I'm not absolutely sure about this values...)
The reason behind this is... not very clear. There is a big anti-terrorism stamp on this rule, but if you question the rule, there is no reasonable answer. You can bring enough toxic substance in that bag to kill everyone on board, or even explosives to put the aircraft down.
If you ask me, the entire rule is there because the authorities wanted to make a rule to demonstrate that they are taking action. Remember that liquid baby food and personal medicine is excluded from the rule. Do you think terrorists would not abuse these exceptions? I still think this was the biggest coup ever of cosmetics and plastic bag sellers... (The latter could advertise explosion-proof bags... )

Sorry, I went a bit off-topic.
In general, it's easy to check carry-on luggage for liquids, as they (or their cans) are clearly visible on X-rays.
Explosive or oxidative material like your nitrate- or peroxide compounds are also in general banned from aircraft, from carry-on as well as from checked baggage.
However, they are hard to see on X-rays, especially if you put them into a less obvious shape. Manual inspection of your luggage would be the only way to search for these substances. In case of doubt, the staff at the safety check can do a wipe test, which means they wipe a small, special card over your carry-on (also from inside, and may be, they also check you). The card is then inserted into an analysis device, which can identify traces of forbidden substances, like explosives and drugs.
Here is a picture of a wipe test, with the analyzer in the background:

Demonstration of wipe test. Source: http://noe.orf.at
I remember flying from Zürich with a bag full of electronics. (Laptop, Laptop charger, mouse, another mouse, headphones, camera, camera charger, camera-to-laptop-cable, custom PCB, ...) and they did a very, very, really very careful wipe test.

Security theatre

Actually, the limit is officially 100 mL in the U.S., too. The 3 fl. oz. part is just an approximation used for purposes of being more useful to most U.S. passengers who are more accustomed to fl. oz. than mL and whose products are more likely to be labeled in fl. oz. than mL.


text:
What is the maximum altitude allowed to fly a model plane/copter in Germany?
What is the maximum altitude I'm allowed to fly a model plane or 'copter in Germany?

I think it depends on which flight rules you are under (VFR, IFR?) and the classification of german airspace. If you provide some more context someone will be able to provide the exact figures.

@orique: A model plane.

@janhudec oops, I must read twice...

You might want to generalize the question to what regulations you have to follow. There may be other restrictions regarding flying close to airports and such.

The closest airport is around 70km away... (it's military too if it makes a difference)

You need to consider the local airports too and with those I doubt place that is 70km away from nearest airport even exists in Germany. Though what really matters is the airspace classes.

The maximum altitude you can operate your RC plane or copter vertically without any clearance from ATC or another government body is the upper limit of class G airspace in Germany, which is the first available airspace from GND to the lower vertical limit of controlled airspace C/D/E, which can be 2.500ft AGL1, 1.700ft AGL or 1.000ft AGL, depending on surrounding airspace and airports in the vicinity. You can register at the website of the DFS AIS to obtain the ICAO charts for your area and take a look at the airspace structure near you.
The actual ceiling of airspace G can be significantly lower in the vicinity of larger airports, where the controlled airspace C/D/E has been lowered. The below picture shows how the dark green section around Frankfurt Airport has an airspace C with the vertical limits 1.500ft (MSL)/FL100. The airspace E in that area (not visible in this picture) has a vertical limit of 1.000ft AGL/C. Some areas within that section already have an elevation of 700-1100ft MSL, which leaves less than 100-400ft of airspace G before the overlying airspace C begins.

If you want to get your RC plane or copter into class C/D/E airspace, which is controlled airspace, you will need to obtain a clearance through the ATC unit in control of the sector or the FIS sector responsible, as postulated in LuftVO §16a

§ 16a LuftVO
  Besondere Benutzung des kontrollierten Luftraums
  (1) Bei Inanspruchnahme des kontrollierten Luftraums ist von der zuständigen Flugverkehrskontrollstelle eine Flugverkehrskontrollfreigabe einzuholen für
  1. Fallschirmsprünge und den Abwurf von Gegenständen an Fallschirmen;
  2. Aufstiege von Flugmodellen und anderen fern- oder ungesteuerten Flugkörpern mit Eigenantrieb;
3. Aufstiege von unbemannten Freiballonen mit einer Gesamtmasse von Ballonhülle und Ballast von mehr als 0,5 kg sowie Aufstiege von gebündelten unbemannten Freiballonen und Massenaufstiege von unbemannten Freiballonen.

Please also mind LuftVO §15a, which dictactes that any RC plane or UAV needs to remain within the visbility range of the controller, so the maximum altitude can vary depending on the size of your RC plane or copter, the weather minima at your location and your own eyesight:

(3) Der Betrieb von unbemannten Luftfahrtsystemen ist verboten, wenn

  1. er außerhalb der Sichtweite des Steuerers erfolgt oder
  2. die Gesamtmasse des Geräts mehr als 25 Kilogramm beträgt.

1: AGL = Above Ground Level
2: MSL = Mean Sea Level

Future readers should be careful, due to the increased usage of quadcopter drones and first reports about incidences with them emerging, this is about to change.
The currently proposed draft for a new law adds requirements like:

strict altitude restrictions
plaque stating the name and address of owner/operator
drone pilot license

depending on the starting weight of the drone / RC model (in the following UAVs for unmanned aerial vehicle).
Because this has (to my knowledge) not been decided conclusively, here's an example as to how I remember a TV news report on the law's current draft:

UAVs up to 250g starting weight, 100m max altitude, no plaque or license needed
UAVs above 250g starting weight, 100m max altitude, plaque indicating name and address but no license needed
UAVs above 5-10kg (I'm really unsure about this number) additional license needed but altitude restriction is regulated according to airspace classification, which is taught in the process to acquire the license.

I bolded what I think will be the answer applying to OP in a few months time.
In close proximity to airports you're already disallowed to fly anything unless you have license and ATC clearing.

If you have more concrete info, feel free to edit the post, e.g. with sources, when the law has passed legislation. Please keep in mind this all applies to Germany.

The problem about this answer is that, as you say, this is about a proposed draft, that could change endless times before turning into law (if it will ever do). You should post it when and if the law is actually passed.

I do understand that criticism. One side of the problem is, "current" answers may very well be obsolete in a few months. After all there's no lobby concerned. Political parties have no reason to care about the finer details. It's just not controversial enough to raise a big discussion. The other side of the problem is, my "answer" isn't really an answer. It is basically an IANAL disclaimer. It doesn't help unless it raises awareness about the limits of QA sites. Plus, I can't promise to notice the end of legislation process, come back and find a 3 year old QA. Of course, I can't expect upvotes

You're just listing reasons for which you should not have posted, as I see it. current answers may become be obsolete -> let's worry about that when and if that happens. my answer isn't really an answer glad you see that. I can't promise to notice the end of legislation process, come back and find a 3 year old QA well, nobody asked you to do that until you posted this.

You're right. Here's the sole reason, I posted: I thought it is important to know that 3 year old answers are not reliable information. To add to that I wrote a rough guideline when a reader needs to search for more info on his/her own. After all if I'd google, find this QA and read everything but my answer then I'd think that's all I need to know. Which is simply not true. Feel free to delete the answer and these comments, if you disagree.

Try this link: http://www.rc-network.de/magazin/artikel_02/art_02-0001/art_02-0001-00.html#3.  If you want an even broader view, go to this link here: http://www.rc-network.de/magazin/artikel_02/art_02-0001/art_02-0001-00.html.  Hope this helps!
This is a quote from the first link:

Basically, it can be stated that the model airplane at the latest at
  FL 100 (FL = flight level, flight level), which is about 3 km above
  sea level, comes to an end.

The page is in German, and of course, Chrome didn't provide a perfect translation.  So model airplanes aren't allowed to fly higher than 3 km.  Higher airspace is reserved for commercial flights, military, etc.

Please show the pertinant information in your answer and not just links. Links break, but if you quote the actual information, it will be a better answer.

The answer should also be incorrect, as model planes cannot enter class E to my knowledge. I'll hunt down the relevant articles from the LuftVO later tonight and post an answer. You also cannot operate RC planes or drones outside your own visibility range.